POS1241 IMAGING OF INFLAMMATION IN THE CONTEXT OF MYOPATHIES USING A NEAR-INFRARED FLUORESCENCE-BASED METHOD - A POSSIBILITY FOR THE DIAGNOSTIC SUPPORT OF POST-ACUTE SYMPTOMS AFTER VIRUS-RELATED DISEASES?
Authors: P. Welker, D. Franke, A. Briel, V. Failli
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Myopathies with main symptoms of muscle pain and weakness can have a wide variety of triggers, be characterized by different courses and localizations, and occur as side effect of rheumatic diseases. They have also recently come into focus as sequelae after systemic viral infections, for example as post-acute Covid-19 syndrome. Inflammatory reactions (Polymyositis, PM) are often difficult to differentiate from non-inflammatory myalgias. Clinical examinations and analysis of serum parameters are helpful, but do not always lead to clear results due to overlapping syndromes. In addition to pathogen-related myositis (Lyme disease, LD), muscle inflammation can also occur in autoimmune-caused rheumatic diseases such as systemic sclerosis (SSc), rheumatoid arthritis (RA), or polymyalgia rheumatica (PMR). Furthermore, overexertion, degeneration, or psychosomatic influences (fibromyalgia, FM) can lead to the symptom of muscle pain. <h3>Objectives</h3> The present work investigates the potential of NIR-FOI feature assessment in diagnosing patients with muscle weakness and muscle pain to better explore therapy options. <h3>Methods</h3> NIR-FOI analyses of patients (n = 200) without clinical symptoms (Ref, n = 31), or the diagnosis of osteoarthritis (OA) (n = 35) were compared with PM patients (n = 9), and patients diagnosed with autoimmune RA (n = 35), SSc (n = 34), Sjögren Syndrome (SS, n = 20), or PMR (n = 5). In addition, patients with diagnoses of LD or primary FM (n = 31) were examined. Indocyanine green as fluorescence dye was injected and the FOI images of both hands were evaluated from 0-240s (Prima Vista Image, PVI), or in the late period P3 (150-240s). Signal intensities (SI) were created from the summation images. For characterization of the cohorts, serum parameters were determined. <h3>Results</h3> Since the detection of serum JO-1 antibodies can be considered as reliable evidence of myositis, patients with this verification were examined first. In addition to increase of SI in PVI (p&lt;0.0001), 8/9 PM patients show stronger accumulation in P3 in the anatomical position of hand muscles, and in the tendon-muscle junction of the forearm compared to the Ref group (Figure1). In the cohort of patients with PMR, the PVI SI was also increased (p&lt;0.0001). Stronger P3 accumulation was observed in 3/5 patients. However, besides accumulation in the joints as the main site of inflammation in this disease, signal increase was detected mostly in the muscle-tendon transition, which could be also attributed to degenerative changes due to the high age of this cohort. That is also true for the patients in the OA cohort, but with lower SI both in PVI and P3. In addition, increased PVI SI was detected in all other disease cohorts (p&lt;0.01). However, increased accumulation in P3 can only be detected in some of the patients of these cohorts and predominantly in the muscle-tendon transition. Most frequently, patients with increased accumulation in P3 were identified in the groups of RA and SS. However, increased accumulation in P3 was also detected in 48% of patients diagnosed with fibromyalgia, but only in the muscle-tendon junction. <h3>Conclusion</h3> The study demonstrates that changes in the microcirculation in inflammatory processes in the context of myositis correlate with a late phase dye accumulation during a NIR-FOI examination. This could provide valuable information for differential diagnoses of inflammatory versus non-inflammatory myopathies to optimize therapy. NIR-FOI could also potentially be used for the screening of myositis in virus-related diseases (e.g., Covid-19). <h3>Acknowledgements</h3> Funded by the Federal Ministry of Education and Research (grant nb.; 13GW0341A). <h3>Disclosure of Interests</h3> Pia Welker Employee of: nanoPET GmbH, Danielle Franke Employee of: nanoPET GmbH, Andreas Briel Shareholder of: Xiralite GmbH, nanoPET GmbH, Vieri Failli Employee of: nanoPET GmbH.